Apparatus and process for polishing semiconductor or similar materials

ABSTRACT

In an apparatus for polishing semiconductor material, such as that in wafer form, a turntable is rotatably supported upon a framework, and said turntable is disposed for receiving in a polishing relationship a plurality of hubs, each of which hub is associated with a spindle, with all of said spindles being connected to a relatively free-floating, force distributing plate member; the rotation of said turntable effectively polishing the hub retained wafers, and causing each of said hubs to rotate itself about its own central axis incident to the revolving of said turntable. A height adjusting means supports a force exerting means against the plate member holding the spindles, so that a precise quantity of controlled force is directed upon said hubs during a polishing operation, and tension straps interconnect between said adjustment means and the spindles to retard the simultaneous turning of said spindles and hubs about the center of said turntable, and also eliminate any distorting or tilting forces that are detrimental to uniform and even polishing. Various locating means and guide means are provided in the apparatus to assist in the precise locating of the hubs upon the turntable as during set up, so that said hubs will be in proper alignment with their respective spindles.

United States Patent [191 Cronkhite et al.

[ 1 Jan. 9, 1973 [54] APPARATUS AND PROCESS FOR POLISHING SEMICONDUCTOR OR SIMILAR MATERIALS [75] Inventors: Paul W. Cronkhite, St. Charles; Robert D. Voege, OFallon, both of Mo.; Joseph W. Poletti, Belleville,

ill

[73] Assignee: Monsanto Company, St. Louis, Mo.

[22] Filed: Aug. 17, 1970 [2]] Appl. No.: 64,165

Primary Examiner-Harold D. Whitehead Att0rneyPaul M. Denk and Neal E. Willis 57 7 ABSTRACT In an apparatus for polishing semiconductor material, such as that in wafer form, a turntable is rotatably supported upon a framework, and said turntable is disposed for receiving in a polishing relationship a plurality of hubs, each of which hub is associated with a spindle, with all of said spindles being connected to a relatively free-floating, force distributing plate member; the rotation of said turntable effectively polishing the hub retained wafers, and causing each of said hubs to rotate.itself about its own central axis incident to the revolving of said turntable. A height adjusting means supports a force exerting means against the plate member holding the spindles, so that a precise quantity of controlled force is directed upon said hubs during a polishing operation, and tension straps interconnect between said adjustment means and the spindles to retard the simultaneous turning of said spindles and hubs about the center of said turntable, and also eliminate any distorting or tilting forces that are detrimental to uniform and even polishing. Various locating means and guide means are provided in the apparatus to assist in the precise locating of the hubs upon the turntable as during set up, so that said hubs will be in proper alignment with their respective spindles.

18 Claims, 10 Drawing Figures PATENTEDJAH 9197a 3,708,921

sum 5 [1F 5 &

APPARATUS AND PROCESS FOR POLISHING SEMICONDUCTOR OR SIMILAR MATERIALS BACKGROUND OF THE INVENTION frictional forces that tend to distort and induce uneven lo polishing of, for example, silicon wafers, are alleviated through the control of the various forms of related rotations of the turntable and associated hubs holding the wafers being polished.

The prior art is replete with various and modified forms of grinding or surface lapping machines which are used primarily for abrasively removing rough thickness or for forming a rough surface upon an article such as glass, semiconductor wafers, and similar and related types of materials. In most instances, the article or wafer to be lapped is placed within a plurality of loose dops and laid upon a rotatable abrasive surface, so that when the dops encounter various types of obstructions arranged above the abrasive surface, they are restrained from further movement in a rotatable fashion about the center of the turntable, to thereby achieve primarily a grinding of their held wafers. Such an arrangement, as is very well shown in the prior art, is quite effective in providing for a roughened polished finish upon the surface of the retained wafers, but as a result of the multitude of forces,.and in particular the various forms of frictional forces, that act upon the wafers during the movement they undertake incident to the rotation of the turntable, frequently uneven polishing is the consequence, somewhat a detriment that cannot be tolerated in the precision that is required, for example, in the application of semiconductor wafers in the electronics art. For example, in the case of most industrial grinding or polishing operations, considerable abrasiveness and energy are encountered and expended in their operation, and the coefficient of friction induced through the use of these devices is quite high, oftentimes in the vicinity of 2. Operating a polish- 1 ing apparatus with a coefficient in this range produces high forces'that must be restrained. Essentially, this means that ina polishing operation, the normal force or polishing pressure creates a fictional force in a direction perpendicular to this induced pressure, and such a force can be gauged at approximately twice this normal force exerted upon the wafer. Such an induced force can give rise to other distortions, such as creating a vertical component in the frictional force atthe leading edge of the dops where they encounter their obstruction to rotation upon the turntable, consequently causing changes in the polishing pressure, and therefore, in the polishing rate. Such distortions must be resisted to achieve precision polishing. Furthermore, these detrimental forces are in part influence by, and have an effect upon the mechanical linkage or devices supplying these normal or polishing forces. Almost all previous designs in lapping machines depend upon the 7 employment of various types of sliding bearings or pivot bearings to resist the torsional or polishing type forces, but these hearings themselves induce a desultory frictional force that is somewhat opposing to the normal or polishing force. The net result is that the polishing force, which controls the polishingrate, is essentially modified in an uncontrolled fashion by the side or torsional thrust produced through the sliding friction induced during the polishing action. Hence; the torsional forces that are present in these prior art devices,

and which cause a binding upon the holder of the wafer in its relationship upon the turntable, has a tendency to create uneven polishing rates. V

It is, therefore, a principal object of this invention to provide a wafer polishing apparatus wherein the hubs retaining a plurality of wafers are essentially fixed in place by means of spindles, wherein as the, spindles allow for a turning of each hub about its own axis, as induced through the rotation of the turntable, they-otherwise effectively hold each hub stationary and free from rotating about the center of the turntable, and stabil ized against uneven movement or frictional binding upon the turntable polishing surface.

It is another objects of this invention to provide tension straps that effectively fix the wafer retaining hubs and spindles stationary upon the turntable, preventing their skewing during polishing, thereby absorbing or generally resisting the torsional or turning forces that do produce uneven polishing of such wafers, while yet allowing each hub to gradually turn about its own axis incident to the rotation of said turntable.

It is a further object of this invention to provide. a polishing apparatus that incorporates a height adjusting means which dually acts to furnish sufficient clearance as during setting or removal of the wafer bearing hubs upon or from the turntable, while also exerting that degree of downward force upon the hubs to achieve effective and controlled polishing of each wafer during a polishing operation.

It isstill another object of this invention to provide a combination of hub locating and guide means that are conveniently indexed to provide for a precise setting of each wafer retaining hub'upon the turntable as during set up in preparation for a polishing operation. I

Another object of this invention is to provide a polishing apparatus which is mechanically adept in achieving polishing of semiconductor 'or other type wafers, and to a high degree of precision and tolerance.

. Still another object is to provide a method of effectively polishing semiconductor wafers.

Other objects will become apparent to those skilled in the art in the light of the following summary and description of the preferred embodiment.

SUMMARY OF THE INVENTION In the polishing of semiconductor or similar type wafers upon lapping or polishing apparatuses, there are a multitude of various dynamic forces that arise through the interrelationship of the various movable mechanical components that comprise the apparatus. In this invention, the usual polishing apparatus turntable is employed having a polishing pad of that degree of abrasiveness, or more particularly having the characteristics to induce polishing, that is mounted on its surface so as to provide for the fine grinding, or frictional polishing, of the exposed wafer surfaces. Due to the fact that the plurality of wafers being polished are held bya series of hubs, and since these hubs have adiameter that may be only slightly less than the radius of the turntable, obviously there is a tendency on the part of each hub to be induced into rotation about its own axis incident to the turning of the turntable since the frictional forces, accompanying the angular velocity acting I upon the edges of the hubs momentarily located proximate the periphery of the-turntable at any given instance will be slightly greater than the forces of the turntable acting upon the opposite edges of the hubs that are located more towards the center of the turntable. This incidental rotation of the hubs in relation to the rotation of .the turntable, in and of itself,,is not an undesirable feature, since this type of gradual and continu'al turning of the hubs does effectively impart widespread exposure .of each wafer-to all areas of the abrasive or polishing surface of the turntable along its entire contacted radius, which beneficially achieves a uniform polishing of the wafers. On the other hand, in most instances in the prior art, as previously discussed, there is a tendency to also allow the hubs to be independent or partially ride around the center of the turntable during its turning, and when the incident turning of each hub due to the varying angular velocities of the turntable at various points along its radius are combined with this aspect of the additional free rotation ofthehub about the center of the turntable, various angular or..torsional type forces are further induced and subjected'upon the wafers which have a tendency to develop uneven polishing, and in many instances, to tolerancesthat are unacceptable in the electronic trade. Furthermore, wherethere is excessive and uncontrolled freedom of the hubs uponthe turntable,

ends to a relatively free-floating'but rigid plate. To

achievethe proper degree of pressure upon the spindles and hubs, during a polishing action so as to maintain a snug seating ofthe waferbearing'hubs upon the rotating turn-table, aheight adjustment means incorporating a series of fluid pressure actuated cylinders located outside the periphery'oftlie turntable, includes. a force exerting device in the natureof a center loading shaft that may be brought into contact and impress a force upon the center of the free-floating plate, which force] is equalized, disseminated and transmitted through the series of spindles to the hubs and upon the wafers in polishing contact with the polishingpad. On the other'hand, it has already been discussed thatthe torsionalltype force which develops when each hub is allowedto loosely rest upon the turntable has a detrimental effect upon the polishing action, this invention incorporates a seriesof tension straps that aredesigned to be. rigidly affixed to the height adjustment means, and moreparticularly, itsspider type assembly which retains the loading shaft centrally thereof, with each tension strap being mounted preferably to the upper end of a spindle, or its associated free-floating plate, so as to prevent the turning of all of said hubs about the center of the-turntable-as the latter rotatesduringa polishing operation, but more specifically to resist the development of and absorb any torsional forces. Hence, through this combination of elements, while the turntable rotates during a polishing operation, and due to this rotation each hub will have a tendency to rotate about its own central axis or spindle incident to the rotating turntable, said hubs will be restrained by means of these tension straps from rotating about the center of said turntable, and from changing in their seating thereupon. Hence, the only true force then exerted upon the wafers during a polishing operation will be the horizontal or frictional force that develops due to the normal force or weight of the hub and pressure exerted upon it by the center loading shaft, which polishing or frictional force will be uniformly exerted. upon all of the wafers since each hub will also be gradually rotating about its own center or spindle'due to the varying angularforcesrencountered by said hub in its contact upon said turntable. None of the torsional forces that are normally encountered as when thehubs are unsupported in their resting upon the rotating turntable are encountered since the tension straps effectively absorb such forces and restrain the hubs from distorting, or inducing any spurious vertical forces that could change the controlled verticalpolishing load...

More specifically, the combination of the tension straps and the free-floating plate that rigidly connects to each spindle prevents any tilting of a spindle during operation of the apparatus, and through this arrangement tends to equalize and absorb any vertical component of the induced frictional force developed during polishing. Hence,the resultant net force developed duringpolishing is the true frictional or polishing force that is perpendicular to the normal force exerted through the spindles andfree-floating or equalizerplate by meansv ment above the center of each hub andproperly mate.

therewith. Hence, a means for locatinga wafer bearing hub upon the turntable is provided, and a guide means supplements this locating of eachhub so that when it is set upon the, turntable prior to a polishing operation, it

,will be directly in vertical alignment with a spindle arranged thereabove. The hub locatingrneans preferably incorporates a pivotal arm which connects'at one end to a shaft, which shaft may be vertically displaced by means of an air cylinder, and which shaft'contains a camming groove that cooperates with a Imating, follower so that upon a loweringor raising respectively,-'of said shaft, its arm will be pivotedv either into a hub setting relationship contiguously over the turntable; or returned outside the periphery of the turntable as when not in use. This pivotal arm incorporates at theother end an arcuate portion containing a pair of downwardly extending members that may embrace at least two pointsof the periphery of a hub and precisely position the same upon the turntable.

To add further accuracy in the setting up of the hubs upon the turntable for a polishing operation, the guide means comprises a light emitting member which is disposed above the polishing apparatus and focuses a beam of light onto the turntable at the precise location where the center of a hub should be arranged, so that as the spindles are lowered as during regulation of the height adjusting means, each spindle will precisely insert within a mating portion provided in the center of each hub. Furthermore, the polishing apparatus includes an indexing device which provides for, as for example when three hubs are tobe arranged upon the turntable, a turning of said turntable exactly one-third around, or 120, so that both the hub locating device and the guide means or light may be immediately again used in adjusting of both the second and third hubs upon the turntable for quick setup of the polishing apparatus just incipient to its operation.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, FIG. 1 is a plan view of the polishing apparatus of this invention;

FIG. 2 is a front view of the polishing apparatus of this invention, as also disclosed in FIG. 1;

FIG. 3 provides a sectional view taken'along the line 33 of FIG. 1, showing the relationship between a mating hub and spindle, and the center load shaft exerting pressure upon the relatively free-floating or equalizer plate rigidly connecting to the spindles;

FIG. 4 provides a sectional view taken along the line 44 of FIG. 1, showing one fluid pressure actuated cylinder of the height adjusting means of this invention;

' FIG. 5 is a sectional view taken along the line 55 of FIG. 1, showing the cylinder actuated shaft that raises and lowers the shield that surrounds the turntable and hubs as during a polishing operation;

FIG. 6 is a sectional view taken along the line 66 of FIG. 1 showing the fluid pressure actuated cylinder and shaft, including its camming relationship, that operates the pivotal arm of the hub locating means of this invention;

FIG. 7 is a sectional view taken along the line 77 of FIG. 1,showing the relationship of a tension strap interconnecting between an arm of the spider assembly and to a spindle; I '7 FIG. 8 is an illustrative perspective view of the turntable having the hub locating 'means in position for setting a hub,.with the guide means or light focusing upon the center of said hub to aid in its accurate setting;

FIG. 9 is a plan view of a cylinder actuated rack and pinion that is used to index and rotate the turntable a precise number of degrees as during the setting of wafer bearing hubs upon the turntable during set up; and

FIG. 10 provides an illustrative view of hub showing in phantom line the positioning of a series of wafers held by the same.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and in particular FIGS. 1 and 2, there is disclosed in its entirety the polishing apparatus A which includes a framework 1 comprising a series of side and end walls 2 that are structurally supported and braced by structures 3, with a series of adjustable legs 4 holding the framework above the ground level. This framework 1 may also be more descriptively referred to as the lower cabinet assembly, for mounted within its interior are the usual means for providing power to the polishing apparatus, including a motor 5 which connects by means of a belt, shaft, or the like, as at 6, which in turn connects by means of a pulley and shaft to a standard speed reducer 7 that effectively controls the speed of rotation of the polishing turntable 10. This turntable is stably supported upon the reducer by means of the reducer output shaft 8, which supports the drive plate assembly 12 including its adapter hub 13 and driver plate 14 that comprises support of the turntable. A lower shaft 9 connects with means for indexing the rotation of the turntable 10 as during setup. Usually, a turntable when used for polishing purposes will also include a polishing pad 15 that mounts upon the drive plate 14 to form the turntable l0. Ordinarily these polishing pads, which are available from commercial sources, may be formed as a porous polystyrene, or similar type material, which when used in combination with, or impregnated with a polishing or grinding'agent, such as a silicon etchant, will effectively polish the surface of the contiguous wafers, to'a fine degree of precision, without exposing the wafers to that extreme of abrasiveness which is usually encountered in the standard lapping machines. Since this'polishing agent or lubricant is deposited in some quantity upon the turntable during a polishing operation, a troughing assembly 16 is provided around the periphery of the turntable for removal of any excess lubricant. 1

During operation of the polishing apparatus,a series of hubs 17, each holding a series of silicon wafers 18 (see FIG. 10) are resting upon said turntable 10, and

more particularly its polishing pad 15, so that said wafers are in contiguous and polishing contact with said pad. 7

Each hub, when in operative position resting upon the turntable, is engaged by a spindle means 19, which series of spindle means are held a fixed distance apart by rigidly connecting to a relatively free-floating plate or equalizer plate 20. See also FIG. 3. This plate 20 has force exerted'upon it by a height adjusting and polishing load providing device 21 which includes a spider like member 22 having a series of radially disposed arms 23 that mount proximate theftop ends of fluid pressure actuated cylinders 24. As will be subsequently described, the height adjusting means 21 through the actuation of its cylinders 24 furnishes a means for regulating the amount of pressure or force that is exerted upon the plate 20, and consequently through the spindles and hubs as retaining the wafers in contact upon the turntable. To resist any turning of the spindles and hubs about the center of the turntable as the latter rotates during a polishing operation, and to absorb any of the incidental torsional forces that tend to cause distortion during polishing, a series of straps 25 interconnect between the arms 23 and to the spindles, thereby stabilizing the spindles and their associated hubs against rotation, and also tilting by reason of the frictional forces acting upon the wafers. 7

By referring again to FIG. 3, the pressure exerting relationship between the height adjusting means 21 and the spindles l9 and hub -17 is accurately disclosed. Each hub 17 comprises a hold down portion 26 that supports a polishing block 27 to the underside of which a plurality of wafers to be polished are mounted by hesive, and said hub retained wafers rest upon the upper surface of the polishing pad 15, as previously described. Into the upper central portion of each hub is provided an insert 28 which may be constructed of brass or other type of enduring rnaterialso as to accommodate' the downward end .29 of the spindle shaft 30.

retained lubricant. The gasket in addition to this seal is.

useful for retainingthe lubricant within the housing 32 of the spindle means. An upper spindle cap 37 encloses the top portion of the spindle housing 32, and said spindle cap isalso useful for securing a clamp 38 that rigidly affixes one end of the tension strap 25 thereto.

In viewofthe foregoing, it can be seen that although the hub17may be easily pulled loose and disengaged from, the spindle end 29,'while the height adjusting means 21 is 'loweredin place, and exerts a pressure upon the downwardly directed spindles, each spindle will be matingly secured within a hub, and as the turntable rotates, the variations in the linear velocities along the radius of the turntable that are exerted upon the hub also causes a turning, of each hub through the rotating of its respectivespindle shaft 30.

Each spindle is rigidly secured, through anaperture 39 in the equalizer plate by means of a fastener 40. This plate 20,:as previously described, is relatively unsupportedinits relationshipwithin the polishing apparatus, votherthan the support it receives as when the series of connecting spindles are engaged within their particular hubs and resting upon the turntable. At the center of this plate 20 there is located a pressure plate 41 and disposed for bearing upon the surface of said pressure plate is the peened end 42 of a shaft 43. This shaft is secured through the center of the spider assembly 22, of the height adjustingmeans 21, with a bushing 44 providing for snug engagement of the rod therethrough,.and an acorn nut and washer 45 retainingv said shaftand. bushing therein. The relationship I being pressed upon the polishing pador surface 15.

Thus any degree of force maybe exerted upon the wafers by means of this center loading shaft 43 in excess of the individual weight each hub exerts upon the wafers. To provide a means for raising of the spindles as when theheight adjusting means 21 is elevated, a series of screws 47 threadedly engage within the plate '20 proximate each. spindle means, with said screw being loosely disposed; through an aperture 48 provided between the en'd'42 of this shaft, which may be more through an extended tab 49 formed integrally with the spider assembly 22.'Thus, when the height adjustment means 21 is raised, eventually the head of each :screw 47 will encounter the tab 49 and also effect araising of the plate 20 and its associated spindle means 19, disengaging said spindle ends 29 from their respective mating hubs 17. In this manner, the hubs may then be removed and the polished wafers taken, in preparation for set up for another polishingoperation.

"Also extending downwardly from the underside of the plate 20 is a member.50 having a conduit 51 provided ,therethroug'h, with the downward end of said member 50 being in close proximity to the polishing surface 15 when the apparatus is set up for use. Any form of polishing lubricant or polishing agent, such as a silicon etchant, for example, Syton as manufactured. by the Monsanto Company,v may be flowed through the conduit 51 and deposited onto the polishing surface 15 in ample quantity during a polishing operation.

By referring to FIG. 4, in. addition to FIG. 3, it canbe seen that each arm 23 of the spider assembly 22 mounts approximately to the. upper end of a shaft 52, which shaft is disposed for vertical shifting within, a pair of means ofa fastener 55, and secured to the underside of 1 said holder by means of a fastener 56 is a fluid pressure cylinder 57, such as 'anair cylinder, that incorporates a piston58 therein which is shiftable vertically in either direction by means of the entrance or withdrawal of air from the fitting 59. The rod-.60 further stabilizes the support of the cylinder 57 to the holder and framework. Thus, the simultaneous vertical shifting of all of the shafts 52 of the series of fluid pressure actuated cylinders 24 willcause the height adjusting. means to be raised or lowered respectively. A bellows 61 is provided surrounding each shaft 52' of the cylinders'inorder to protect and prevent the entrance of any dirt proximate the area of the bearings 53.

During operation of the polishing apparatus, as when I its turntable rotates, the hubs 17 will be induced into.

their own centralized rotation around each :spindle means "19 due to the rotation of said turntable,and it is desirable to curtail any further movement of said spindies and hubs as about the center of the apparatuslor turntable, and to prevent their distortingdue'to the frictional forces. acting upon them.'To do'this, and. as previously described,a tension'strap 25 interconnects between each arm '23 of the spider assembly, and also to the top of each associated spindle 19. By referring to FIG. 7, the tension strap 25..is secured by the clamp 38 provided on top of each spindle means 19, while the other end of saidstrap is secured'by means of anadditionalclamp 62 to the top of said arm 23. it is noted that the orientation .of each tension strap, as disclosed in FIG. 1, in its connection to the top of its associated spindle, is approximately at a normal to the radius. of

the turntable at that particular underlying position.

' Hence, one of the benefits ofthesestraps is to resist a turning of their particular associated spindles as during rotation of the turntable. Furthermore, these straps balanced by each of the other spindles all through their rigid connection to the free-floating equalizer plate, and in this manner, any vertical component of the frictional force is eliminated, so that the only force being exerted upon each spindle and its associated tension strap is a true horizontal polishing force. During operation of the polishing apparatus, it has been found that the tension straps 25 have a tendency to be subjected to vibrations, and to alleviate such, which otherwise could have a detrimental effect upon the polishing operation, a secondary strap 63 also connects to the clamp 62, and is arranged in overlying relationship to the underlying tension strap 25, with said strap having a cushioning member 64, such as one made of silicone rubber, which rests upon the top of said tension strap 25 and effectively absorbs any vibrations induced therein.

During functioning of this polishing apparatus, it is desirable to provide some shielding around the entire turntable and the prearranged wafer bearing hubs, and therefore, a shield 65', which is shiftable vertically so that during operation it may be disposed surrounding the'turntable and coacting spindles and hubs,'but that following a polishing operation, or during setup, the

shield may be lowered to fully exposed said turntable closed in FIG. 9, so as to allow for the proper disposi tion of the hubs precisely upon the table and in alignment with the axis of each spindle means disposed thereabove. This hub locating device includes a pivotal arm 82 which has integrally formed at one end and arcuate portion 83, see also FIG. 1, that includes a' pair of downwardly depending members, as at 84, that are spaced apart and disposed for a two point contact with 16, as previously described in FIG. 1, is useful for providing drainage of any materials from the conduit 68. The bottom structure 66 further connects with additional bracing 69 that is formed integrally with an arm 70 projecting radially from said shield. This arm 70, atone end, connects by meansv of a fastener 71 to the upper end of a rod 72, which rod attaches at its other end to a piston (not shown) contained within a fluid pressure actuated cylinder 73 securing to the underside of the'framework 1. For the sake of cleanliness a bellows 74 surrounds the rod 72, and contracts and expands with the shifting of said rod.

To stabilize the vertical displacement of the shield 65, an additional rod 75 connects tothe approximate other end of the arm 70, by meansof the fastener 76, and said rod is disposed through a bearing '77 to provide for its smooth shifting in a vertical direction concurrent with the operation of the cylinder 73, and the 1 shifting of the shield 65. A bellows 78 also surrounds this rod to avoid the contact of dirt with the rod and its relationship to the bearing 77. The rod 75 extends through apertures 79 provided through the framework 1 with the downward end 80 of said rod threadedly connected to a balance weight 800 that stabilizes a shifting of said shield. By referring also to FIG. 1, it can be seen that a pair of supplemental guides 81 are provided diametrically of the shield 65 to further stabilize its vertical displacement.

During set up of the various wafer bearing hubs upon the turntable, a hub locating device, as disclosed in detail in FIG. 6, coacts with an indexing device, as disthe periphery of a hub 17 as it is set upon the turntable 10. The other end of said arm 82 connects proximate the top edge of a rod 85, enclosed within a bellows 86, with said rod being disposed downwardly through a bearing 87 secured within a housing 88 that mounts upon a portion of theframework l. A camming groove 89 is provided within the surface of said rod 85, and a follower 90 is fixed within the housing 88, and disposed within the cam, so that as the rod 85 is vertically shifted, thefollower will urge a degree of turning of said rod, to achieve a limited pivotal movement of the arm 82. Hence, when the rod is retracted in the positionas disclosed in FIG. 6, it will have been turned to that degree which allows for its disposition in a hub setting relationship contiguous to the surface .of the turntable, as also disclosed in FIG. 8.'On the other hand, as the rod is urged upwardly, it rises above the turntable while simultaneously clearing its periphery until it becomes disposed in a nonoperative position,as disclosed in FIG. 1. This vertical shifting of'the rod 85 is induced through a fluid pressure actuated cylinder 91 that is secured by means of a series of support rods 92 to the underside of the framework 1, with a cylinder actuated rod 93 being swivally connected by means of a clevis 94 to the downward end 95 of said rod 85. It is also likely that this rod 85 may be actuated by mechanical means for pivoting it about its vertical axes, rather than being shiftable vertically, with the cam and follower relationship providing the necessary raising or lowering to the rod and its associated pivot arm 82 and arcuate portion 83 upon pivoting of said rodas during its use in setup.

In the embodiment of the polishing apparatus as disclosed in FIG. 1, there appears three wafe'rbearing hubs axially disposed under three spindle means, and therefore, when each of these hubs is set upon the turntable prior to a polishing operation, it is essential that they be precisely located upon the turntable prior to the lowering of the spindle means into mating contact with their uppersurfaces, as through alowering of the height adjusting means 21. To achieve this, and

I ble, as previously described, can be used to set a particular hub upon said turntable, it is necessary that the turntable itself, after setting of the first hub, be indexed or turned exactly, in this particular embodiment, so that the next and subsequent hubs may also be set precisely below a mating spindle means. To accomplish this, an indexing device, as disclosed in FIG. 9, also connects to the framework 1, and is arranged for providing that degree of rotation of the lower drive shaft 9 that is essential to provide for this l20 rotation of the turntable during setup. See also FIG. 1. As here disclosed, a pinion 96 is formed partially around, the shaft extension 9 below the speedreducer, and said pinion is disposed for intergearing with a rack 97 that is actuated by a pressure cylinder 98. Upon energization of the cylinder.98,.and the longitudinal shifting of its rack 97, the shaft 9 may be turned, the limits of its turning being controlled by a stop pin 99 which may be con tacted by one end .of the partial pinion 96, while a limit switch 100,having a switcharm 101 disposed for being contacted by one end of the rack 97, may provide for. electrical cutoff of the operation of said rack, and consequent partial rotation of the turntable. Thus, through the operation of this indexing means, in this particular embodiment, when its cylinder 98 is energized, it will beset to provide for a precise 120 rotation of the turntable, and "setting of the next hub 17 upon the turntable through'the use of the pivotal arm 82 of the hub locating device. Obviously, a clutching mechanism, as is commonly used in the art, may be employed so as to disengage the rack and pinion combination andthis indexing device as during normal operation of the turntable. For example, this indexing device and its clutch may belocated asshown below the speed reducing mechanism 7,"so as to allow when needed a periodic operation of this indexing device. Then during operation of the turntable, the clutch may provide for disengagement of the drive shaft 9 from the main drive shaft 8, to allow forcontinuous rotation of the turntable as during performance of the polishing operation.

To add further precision to the locatingof each of the hubs upon the turntable as during set upof. the apparatus a light emitting member 102 may mount to the upward portion of the framework and'focus a beam of light onto the turntable at the precise location where the center of a hub, and in particular, its insert 28, is to mate with the downward engaging end of a spindle. It is desirable when placing a wafer bearing hub upon the turntable in preparation for their polishing, that the hub be precisely'set atthe location where the spindle will directly mate into the insert of the hub. Otherwise, as the. spindles-are broughtdown by the height adjusting means for mating with their respective hubs, if the hubs have been placed in an inaccurate position, the spindleswill not mate with the hubs and restrain them, so that upon starting the turntable rotation, centrifugal force will throw the hubs and mounting plates off of the turntable. This action damages the machine, and destroys the material to be polished. Such malfunctioning is undesirable, and has been rectified in this invention by the combined use of the pivotal arm 82 of the hub locating device, the indexing means, and this ligh emitting guide means.- I 1 Numerous variations in the construction and operation of the polishing apparatus of thisinvention, within the; scope of the appended claims, will occur to those skilled in the art in the light of the foregoing disclosure. The description of the preferred embodiment herein is merely illustrative. i

: Having thusdescribed the invention, what is claimed and desired to be secured by Letters Patent is:

1. In an apparatus for polishing semiconductor or other. materials upon the polishing surface of a turntable rotatably supported ona framework, a plurality of hubs arranged for holding said materials in a polishing relationship upon the surface of said turntable, a force distributing member being relatively free-floating with respect to said turntable having a series of downwardly extending spindle means arranged above said hubs,

each spindle means cooperating with a hub to stabilize it for turning incident to the'rotation of said turntable, said spindle means arranging said hubs in spaced relation to each other upon said turntable, a'force exerting means contacting said force distributing member and arranged for directing a ,force upon said distributing member and through said force'transmitting spindle 1 each tensioning means is subjected to tensioning forces while precluding the centralized rotation of said spindle means, force distributing member, and hubs due to their polishing relationship upon the rotating turntable;

2.:ln an apparatus for polishing semiconductor or othermaterials upon the polishing surface of a turntable rotatably supported on a framework, a plurality of hubs arranged for holding said materials in'a polishing relationship upon the surface of said turntable, a force distributing member including a plate-like member being relatively free-floating with respect tov 'said turntable having a series of downwardly expending spindle means arranged above said hubs, each spindle means cooperating with a hub to stabilize it for turning incident to'the rotation of said turntable, said spindle means arranging said hubs in spaced relation to'each other upon said turntable, a force exerting means co-ntacting said plate member and through said force trans mitting spindle means to adjust the amount of pressure being directed by said hubs on the retained materials being polished upon the turntable, a height adjustment means, said means incorporating said. force exerting means, said height adjustment means capable of bringing said forceexerting means into contact with said plate member and upon adjustment providing for a variation in the degree of force being exerted by said force exerting means upon said plate member, said height adjustment means mounts upon, the framework, said adjustment means comprising a multi-armmember having-a series of arms extending radially from the associated force exerting-means, a seriesof cylinder actuated rod members operatively mounted to said framework, theapproximate upper end of each rod being connected tothe extended end, of an arm, said force exerting means being a loading shaft mounted approximately to the center of said multi-arm member withthe downward end of'said shaft disposed forpressing upon said plate member, the operation of said cylinder actuated rod members in one direction providing for disengagement of; said loading shaft fromthe plate member, and the operation of said rodmembe'rs in the opposite direction producing a pressure exertingv relationship of said shaft upon the plate member and associated hubs.

3. The invention of claim 2 and including strap means interconnecting between each-arm and a spindle means, and during operation of said apparatus each strap being subjected to tensioning forces while precluding the centralized rotation of ,said spindle means, plate member and hubs due to their polishing relationship upon the rotating turntable.

4. The invention of claim 3 and including a supplemental strap connectingproximate each arm, said supplemental strap overlying a portion of an associated tension strap that also connects to said arm, means connecting to the overlying portion of said supplemental strap and resting upon said tension strap to absorb any mechanical vibrations induced in said latter strap due 7 to the operation of the polishing apparatus.

5. The invention of claim 3 wherein each strap means connects to a spindle at a position located above the approximate midpoint of the radius of said turntable, said strap means being arranged at approximately a normal to the turntableradius at this point of connection to effectively resist a centralized rotation of said hubs and reduce any uneven polishing generally caused through development of distorted forces existing between the hubs and the rotating turntable.

6. in an apparatus for polishing semiconductor or other materials upon the polishing surface of a turntable rotatably supported on a framework, a plurality of hubs arranged for holding said materials in a polishing relationship upon the surface of said turntable, a force distributing member being relatively free-floating with respect to said turntable having a series of downwardly extending spindle means arranged above said hubs, each spindle means cooperating with a hub to stabilize it for turning incident to the rotation of said turntable, said spindle means arranging said hubs in spaced relation to each other upon said turntable, a hub locating means for arranging said hubs upon the turntable during set up of the apparatus, said means combining a guide means for use in providing precise setting of a hub upon a turntable, and an indexing means operatively associated with said turntable providing for limited turning of said turntable to allow for a precise setting of additional hubs under their respective spindle means through the cooperative usage of said guide means.

7. The invention of claim 6 wherein said guide means includes a light emitting member for focusing a beam of light onto the turntable at the precise location where the center of a hub is to be located.

8. The invention of claim 6 wherein said guide means includes a pivotal arm, said arm having means provided on one end for use in positioning of a hub upon the turntable, said arm connecting at its other end to a shaft, said shaft being mounted for' limited pivotal movement uponsaid framework, means for imparting movement to said shaft, the pivoting of said shaft to its limit in one direction locates the means for positioning of a hub upon the turntable, and the pivoting of said shaft to its limit in the other direction clears said arm and'means from interference with the positioned hubs and turntableas during operation of the polishing apparatus. l 9. The invention of claim 8 wherein the means imparting movement to said shaft shifts said shaft in a vertical direction, the lowering of said shaft induces a pivoting of its arm and operative positioning of the means for arranging of a hub upon the turntable, with said positioning means being brought'into proximity with the turntable, the raising of said shaft induces its pivoting in the opposite direction and clears its arm and positioning means from interference with the arranged hubs and turntable as during operation of the polishing apparatus.

- necting to said framework and disposedfor riding in said track, whereby the raising of said shaft effects its pivoting in one direction, and a lowering of said shaft effects its pivoting in the opposite direction.

11. The invention of claim 9 wherein the means imparting movement to said shaft comprises a fluid pressure actuated cylinder.

12. The invention of claim 8 wherein the means imparting pivotal movement to said-shaft is motor actuated, elevating means cooperating between said pivotal shaft and framework wherein the pivoting of said shaft for locating the means for positioning of -a hub induces a lowering of said means into proximity with the turntable, and the pivoting of said shaft in the opposite direction effects a raising of said positioning means and its clearance from the turntable.

13. The invention of claim 12 wherein said elevating means includes a helical like cam track provided on said pivotalshaft, and a fixed follower connecting to said framework and disposed for riding within said cam track.

14. The invention of claim 8 wherein the means provided on the end of said arm for positioning a hub includes an integral arcuate portion, downwardly extending members connecting to said portion, said members disposed for embracing the periphery of a hub to provide for its location as when said shaft is pivoted into operative position over the turntable. I

15. The invention of claim 6 wherein a motor actuated shaft supports said turntable for rotation, said indexing means includes a pinion integrally connecting upon a lower extending shaft, a rack engaging said memberwhereby each hub is arranged for rotation about its own center incident to the rotation of said turntable, arranging a height adjustment means incor- I porating a force exerting means above said plate member for directing a downward force upon said hubs, affixing a tension strap in a restraining relationship between each spindle and the heightadjustment means to prevent the rotation of each hub about the center of. the turntable, and thereafter rotating the turntable to effect the polishingoperation. 1

17. in the process of claim 16 and including positioning a guide means in proximity over the turntable at the precise location where the periphery of a semiconduc tor retaining hub is to be set upon said turntable, and placing a hub against said guide means and upon the turntable in direct alignment under a cooperating spindle means, thereafter indexing said turntable in partial rotation to provide for a like setting of subsequent hubs equally spaced apart upon said turntable.

a pair of 18.2 In the process of claim 17 including focusing a beam of light onto the turntable at the precise location where the center of each hub is to be set. 

1. In an apparatus for polishing semiconductor or other materials upon the polishing surface of a turntable rotatably supported on a framework, a plurality of hubs arranged for holding said materials in a polishing relationship upon the surface of said turntable, a force distributing member being relatively free-floating with respect to said turntable having a series of downwardly extending spindle means arranged above said hubs, each spindle means cooperating with a hub to stabilize it for turning incident to the rotation of said turntable, said spindle means arranging said hubs in spaced relation to each other upon said turntable, a force exerting means contacting said force distributing member and arranged for directing a force upon said distributing mEmber and through said force transmitting spindle means to adjust the amount of pressure being directed by said hubs on the retained materials being polished upon the turntable, and tensioning means interconnecting between each spindle means and the force exerting means whereby during operation of said apparatus each tensioning means is subjected to tensioning forces while precluding the centralized rotation of said spindle means, force distributing member, and hubs due to their polishing relationship upon the rotating turntable.
 2. In an apparatus for polishing semiconductor or other materials upon the polishing surface of a turntable rotatably supported on a framework, a plurality of hubs arranged for holding said materials in a polishing relationship upon the surface of said turntable, a force distributing member including a plate-like member being relatively free-floating with respect to said turntable having a series of downwardly expending spindle means arranged above said hubs, each spindle means cooperating with a hub to stabilize it for turning incident to the rotation of said turntable, said spindle means arranging said hubs in spaced relation to each other upon said turntable, a force exerting means contacting said plate member and through said force transmitting spindle means to adjust the amount of pressure being directed by said hubs on the retained materials being polished upon the turntable, a height adjustment means, said means incorporating said force exerting means, said height adjustment means capable of bringing said force exerting means into contact with said plate member and upon adjustment providing for a variation in the degree of force being exerted by said force exerting means upon said plate member, said height adjustment means mounts upon the framework, said adjustment means comprising a multi-arm member having a series of arms extending radially from the associated force exerting means, a series of cylinder actuated rod members operatively mounted to said framework, the approximate upper end of each rod being connected to the extended end of an arm, said force exerting means being a loading shaft mounted approximately to the center of said multi-arm member with the downward end of said shaft disposed for pressing upon said plate member, the operation of said cylinder actuated rod members in one direction providing for disengagement of said loading shaft from the plate member, and the operation of said rod members in the opposite direction producing a pressure exerting relationship of said shaft upon the plate member and associated hubs.
 3. The invention of claim 2 and including strap means interconnecting between each arm and a spindle means, and during operation of said apparatus each strap being subjected to tensioning forces while precluding the centralized rotation of said spindle means, plate member and hubs due to their polishing relationship upon the rotating turntable.
 4. The invention of claim 3 and including a supplemental strap connecting proximate each arm, said supplemental strap overlying a portion of an associated tension strap that also connects to said arm, means connecting to the overlying portion of said supplemental strap and resting upon said tension strap to absorb any mechanical vibrations induced in said latter strap due to the operation of the polishing apparatus.
 5. The invention of claim 3 wherein each strap means connects to a spindle at a position located above the approximate midpoint of the radius of said turntable, said strap means being arranged at approximately a normal to the turntable radius at this point of connection to effectively resist a centralized rotation of said hubs and reduce any uneven polishing generally caused through development of distorted forces existing between the hubs and the rotating turntable.
 6. In an apparatus for polishing semiconductor or other materials upon the polishing surface of a turntable rotatably supported on a framework, a plurality of hubs arranged for holding saiD materials in a polishing relationship upon the surface of said turntable, a force distributing member being relatively free-floating with respect to said turntable having a series of downwardly extending spindle means arranged above said hubs, each spindle means cooperating with a hub to stabilize it for turning incident to the rotation of said turntable, said spindle means arranging said hubs in spaced relation to each other upon said turntable, a hub locating means for arranging said hubs upon the turntable during set up of the apparatus, said means combining a guide means for use in providing precise setting of a hub upon a turntable, and an indexing means operatively associated with said turntable providing for limited turning of said turntable to allow for a precise setting of additional hubs under their respective spindle means through the cooperative usage of said guide means.
 7. The invention of claim 6 wherein said guide means includes a light emitting member for focusing a beam of light onto the turntable at the precise location where the center of a hub is to be located.
 8. The invention of claim 6 wherein said guide means includes a pivotal arm, said arm having means provided on one end for use in positioning of a hub upon the turntable, said arm connecting at its other end to a shaft, said shaft being mounted for limited pivotal movement upon said framework, means for imparting movement to said shaft, the pivoting of said shaft to its limit in one direction locates the means for positioning of a hub upon the turntable, and the pivoting of said shaft to its limit in the other direction clears said arm and means from interference with the positioned hubs and turntable as during operation of the polishing apparatus.
 9. The invention of claim 8 wherein the means imparting movement to said shaft shifts said shaft in a vertical direction, the lowering of said shaft induces a pivoting of its arm and operative positioning of the means for arranging of a hub upon the turntable, with said positioning means being brought into proximity with the turntable, the raising of said shaft induces its pivoting in the opposite direction and clears its arm and positioning means from interference with the arranged hubs and turntable as during operation of the polishing apparatus.
 10. The invention of claim 9 and including a helical like cam track provided on said shaft, a follower connecting to said framework and disposed for riding in said track, whereby the raising of said shaft effects its pivoting in one direction, and a lowering of said shaft effects its pivoting in the opposite direction.
 11. The invention of claim 9 wherein the means imparting movement to said shaft comprises a fluid pressure actuated cylinder.
 12. The invention of claim 8 wherein the means imparting pivotal movement to said shaft is motor actuated, elevating means cooperating between said pivotal shaft and framework wherein the pivoting of said shaft for locating the means for positioning of a hub induces a lowering of said means into proximity with the turntable, and the pivoting of said shaft in the opposite direction effects a raising of said positioning means and its clearance from the turntable.
 13. The invention of claim 12 wherein said elevating means includes a helical like cam track provided on said pivotal shaft, and a fixed follower connecting to said framework and disposed for riding within said cam track.
 14. The invention of claim 8 wherein the means provided on the end of said arm for positioning a hub includes an integral arcuate portion, a pair of downwardly extending members connecting to said portion, said members disposed for embracing the periphery of a hub to provide for its location as when said shaft is pivoted into operative position over the turntable.
 15. The invention of claim 6 wherein a motor actuated shaft supports said turntable for rotation, said indexing means includes a pinion integrally connecting upon a lower extending shaft, a rack engaging said pinion durinG indexing of the turntable, means for longitudinally shifting said rack whereupon the shifting of said rack induces a limited turning of said turntable to allow for the spaced positioning of said hubs upon the turntable and under an associated spindle means.
 16. In the process of polishing a series of semiconductor wafers or other material upon a turntable rotatably supported upon a framework, positioning a series of wafer retaining hubs upon the polishing surface of the turntable, engaging each hub with a spindle means that connects to a force distributing plate member whereby each hub is arranged for rotation about its own center incident to the rotation of said turntable, arranging a height adjustment means incorporating a force exerting means above said plate member for directing a downward force upon said hubs, affixing a tension strap in a restraining relationship between each spindle and the height adjustment means to prevent the rotation of each hub about the center of the turntable, and thereafter rotating the turntable to effect the polishing operation.
 17. In the process of claim 16 and including positioning a guide means in proximity over the turntable at the precise location where the periphery of a semiconductor retaining hub is to be set upon said turntable, and placing a hub against said guide means and upon the turntable in direct alignment under a cooperating spindle means, thereafter indexing said turntable in partial rotation to provide for a like setting of subsequent hubs equally spaced apart upon said turntable.
 18. In the process of claim 17 including focusing a beam of light onto the turntable at the precise location where the center of each hub is to be set. 